The present invention relates to a liquid-filled type vibration isolator having a vibration isolation mechanism formed so as to isolate vibrations in a specific frequency area, and more particularly to a liquid-filled type vibration isolator in which an orifice for isolating vibrations between two frequency areas such as, for example, between engine idling vibrations and engine shakes is provided at a partition member for partitioning between the main chamber and the sub-chamber.
Of the vibration isolators, particularly an automotive engine mount or the like must be able to cope with a wide range of frequencies because an engine, which is a power source, is used under various conditions from an idling operating state to the maximum rotating speed. Therefore, there has been devised a liquid-filled type vibration isolator having a vibration isolation mechanism, in which there are provided two liquid chambers within, those liquid chambers are coupled through an orifice and liquid in the liquid chambers is caused to be vibrated at a specific frequency, and has been known already. Of such liquid-filled type vibration isolators, as a type having two orifices, there are an invention disclosed in JP-A-5-272575 specification, or the like.
Then of vibration isolators of the type having two orifices including the above described conventional one, as the negative pressure introduction type liquid-filled type vibration isolator as shown in, for example, in FIG. 5, there is a vibration isolator configured by: a rubber-like insulator 10 integrally having a first coupling member 90 to be coupled to the vibration member side such as the engine, or the like; a member 20 having an adjustment orifice 210, for partitioning between the main chamber and a third liquid chamber; a second diaphragm 30 for partitioning and forming a portion of a balance chamber 330, in which negative pressure is to be introduced, and which operates by the introduction of negative pressure; a partitioning chamber 40 for contributing to the formation of the above described balance chamber 330, made of a rigid-like member; a diaphragm 50 provided below the partitioning member concerned 40, for contributing to the formation of the sub-chamber; or the like. Each of these components is integrally assembled as shown in FIG. 5 to thereby form a liquid-filled type vibration isolator.
Therefore, components (members), each having a complicated shape, including a member 20 having an adjustment orifice 210 or the like are required, and it is inevitable that the cost will be entirely increased. In order to solve these problems, a plurality of functional units including the above described two orifices are arranged to be brought together at partitioning members to be formed by castings made of aluminum alloy. Thus, it is an object according to the present invention to provide a liquid-filled type vibration isolator of the type having two orifices capable of reducing the manufacturing cost as a whole by simplifying the structure of the other components.
That is, according to the invention as specified in claim 1, there is provided a liquid-filled type vibration isolator of a type having two orifices, comprises: a first coupling member to be mounted to a vibration member; a second coupling member to be mounted to a vehicle body-side member or the like; a rubber-like insulator interposed between these first and second coupling members, for absorbing and isolating vibrations from the vibration member; a main chamber, whose chamber walls are formed by a portion of the insulator concerned, and which is filled with liquid; a sub-chamber, whose chamber walls are partially partitioned and formed by the first diaphragm, coupled to the main chamber concerned through the first orifice; a partitioning member for partitioning between the main chamber and the sub-chamber; a second orifice for coupling the main chamber to a third liquid chamber; or the like, wherein the above described partitioning member is configured such that it has a cylindrical shape, has the first and second orifices on the peripheral edge portion thereof, has, on the upper portion side, an opening to be formed independently of the first and second orifices, has a recess, whose bottom portion forms a partition with the sub-chamber, and further has, on its lower portion side, an opening of the first orifice connected to the sub-chamber. With such a configuration, a vibration isolator according to the present invention is to be formed in a state in which each functional unit including two orifices is integrally brought together at the above described partitioning member. Therefore, with such a partitioning member as a basis, an insulator made of a rubber-like member, various diaphragms or the like is installed around the partitioning member, whereby it becomes possible to comparatively simply form a liquid-filled type vibration isolator of the type having two orifices.
Next, the present invention is characterized by the configuration of the third liquid chamber. That is, according to the present invention, there is provided the above described liquid-filled type vibration isolator configured such that within the recess of the partitioning member, there is provided the second diaphragm, which forms a portion of the third liquid chamber, and on the upper portion side where the second diaphragm has been provided, there is provided a lid member, which forms a portion of the third liquid chamber and partitions with the main chamber, thereby the third liquid chamber is integrally formed with the partitioning member as the basis.
With such a configuration, in a vibration isolator according to the present invention, the upper opening of the partitioning member will be blocked up by a simple lid member, thereby it becomes possible to form the third liquid chamber and to integrally form the vibration isolation mechanism of the type having two orifices around the partitioning member.
Next, the present invention is characterized by the configuration of the adjustment orifice, which is the second orifice to be provided between the main chamber and the third liquid chamber. That is, according to the present invention, there is provided a liquid-filled type vibration isolator configured such that within the recess of the partitioning member, there is provided the second diaphragm, which forms a portion of the third liquid chamber; and on the upper portion side where the second diaphragm has been provided, there is provided a lid member, which forms a portion of the third liquid chamber and partitions with the main chamber, whereby a vibration isolation mechanism consisting of the second diaphragm, the third liquid chamber for adjusting the liquid pressure within the main chamber by the operation of the second diaphragm, the second orifice or the like is caused to be integrally formed with the partitioning member as the basis. With such a configuration, in a vibration isolator according to the present invention, the second orifice is formed, and the adjustment orifice, which functions mainly at the input of idling vibrations, is to be provided at the above described partitioning member. Therefore, there is no need for the provision as a separate component unlike a conventional one, but it becomes possible to reduce the manufacturing cost as a whole. In other words, the upper opening of the partitioning member will be blocked up by a simple lid member, whereby it becomes possible to integrally form the vibration isolation mechanism including the third liquid chamber around the partitioning member.
Further, the present invention is characterized by the shape of each orifice. That is, according to the present invention, there is provided a liquid-filled type vibration isolator configured such that the second and first orifices are provided in series to the main chamber. With such a configuration, it becomes possible to sufficiently secure the effective length of the orifice aimed at vibration damping of engine shakes, thus making it possible to secure sufficient damping characteristics.
In addition, the present invention is characterized by the shape of each orifice. That is, according to the present invention, there is provided a liquid-filled type vibration isolator configured such that the first orifice and the second orifice are provided in parallel to the main chamber. With such a configuration, a vibration isolator according to the present invention will be able to effectively damp idling vibrations and vibrations due to engine shakes.